The use of current loops enables the most popular, safe and easy method of transmitting a process variable to a distance limited only by the electromotive force (EMF) that drives the loop. A current loop's simple, two-wire connection allows for fast and simple interconnection to as many devices in the loop (in series) as desired, limited only by the loop's EMF.
Traditional current-loop controllers are externally powered through AC Mains or direct current voltage. They are expensive, complex and bulky. It is desirable, then, to provide a current-loop controller that avoids these shortcomings and that has other advantages as described below. The control circuit should, in addition to driving desired devices, be able to provide, control, and/or indicate outputs and control or manage processes.